In the East End of London, more than a mile from St Paul's Cathedral, and lying near to the docks, there is a tangled knot of narrow streets and lanes, crossing and running into one another, with blind alleys and courts leading out of them, and low arched passages, and dark gullies, and unsuspected slums, hiding away at the back of the narrowest streets; forming altogether such a labyrinth of roads and dwellings, that one needs a guide to thread a way among them, as upon pathless solitudes or deserts of shifting sands.